[dev] Locally built Multipass picks up centrally installed Qt libs and crashes

[ricab]

Describe the bug
Locally built Multipass picks up centrally installed Qt libs instead of vcpkg ones and crashes. Stacktrace:

Thread 33 "QNetworkAccessM" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fff937fe6c0 (LWP 870434)]
0x00007ffff283089c in ?? () from /usr/lib/x86_64-linux-gnu/qt6/plugins/tls/libqopensslbackend.so
(gdb) where
#0  0x00007ffff283089c in ??? () at /usr/lib/x86_64-linux-gnu/qt6/plugins/tls/libqopensslbackend.so
#1  0x00007ffff2830b65 in ??? () at /usr/lib/x86_64-linux-gnu/qt6/plugins/tls/libqopensslbackend.so
#2  0x00007ffff7d7cd31 in QSslSocketPrivate::~QSslSocketPrivate() () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#3  0x00007ffff7d7ce35 in QSslSocketPrivate::~QSslSocketPrivate() () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#4  0x00007ffff7d6f3b5 in QSslSocket::~QSslSocket() () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#5  0x00007ffff7d15806 in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#6  0x00007ffff7d15a35 in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#7  0x00007ffff7d2518c in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#8  0x00007ffff7c7448e in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#9  0x00007ffff7c747f7 in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#10 0x00007ffff7d259bd in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#11 0x00007ffff750f7b2 in QThreadStorageData::finish(void**) () at /lib/x86_64-linux-gnu/libQt6Core.so.6
#12 0x00007ffff75028b0 in ??? () at /lib/x86_64-linux-gnu/libQt6Core.so.6
#13 0x00007ffff75068f7 in ??? () at /lib/x86_64-linux-gnu/libQt6Core.so.6
#14 0x00007ffff6aa3d64 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:448
#15 0x00007ffff6b373bc in __GI___clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:78

There appears to be some sort of mismatch with respect to OpenSSL. There have been similar problems in the past; see #4529, which was replaced by #4530.

To Reproduce
Just follow build instructions (which install qt with apt) and attempt to run the daemon.

Additional info

• OS: Ubuntu 25.10
• CPU architecture or model: x86
• multipass version: 1.17.0-dev.1458+g7f143fd8